U.K. Prime Minister David Cameron said Saturday that Britain's 10 crown dependencies and overseas territories—including financial centers like the Cayman Islands, Bermuda and Jersey—will sign an international convention to help combat tax evasion.

Together with advancing free trade and increasing corporate transparency, combating tax evasion and avoidance is among the priorities of Britain's presidency of the Group of Eight nations this year. Mr. Cameron is due to host a G-8 summit, with leaders of the U.S., Japan, Germany, Russia, France, Italy and the European Union, on Monday and Tuesday in Northern Ireland.

The leaders of the overseas territories and crown dependencies agreed to sign the Multilateral Convention on Mutual Administrative Assistance in Tax Matters following meetings with Mr. Cameron on Saturday. The convention is led by the Organization for Economic Cooperation and Development and has been signed by more than 50 nations.

The crown dependencies and overseas territories—Bermuda, British Virgin Islands, Cayman Islands, Gibraltar, Anguilla, Montserrat, Turks and Caicos Islands, Jersey, Guernsey and the Isle of Man—also agreed to produce action plans about providing information on who owns which companies and who benefits, the so-called beneficial ownership, Mr. Cameron said.